1. Field of the Invention
The present invention relates to an LED chip (hereinafter referred to as “light-emitting element”) in which a light-emitting layer is formed on a substrate, and light is emitted from the light-emitting layer in response to a voltage applied thereto.
2. Description of the Related Art
In a light-emitting element, for example, a GaAs-based crystal layer or the like is epitaxially grown on a GaAs crystal substrate or the like so that a light-emitting layer is formed. When electrodes of an anode and a cathode are provided and a voltage is applied therebetween, light is emitted from the light-emitting layer, and the light is radiated from the top surface (light-emitting surface).
However, in a light-emitting element, a crystal layer including a light-emitting layer is generally high in refractive index, and also high in absorptance of emitted light. Thus, there has been a problem that the efficiency of extracting light from the light-emitting element is low. That is, of light emitted from a light-emitting layer, only light incident on a top surface (light-emitting surface) within a critical angle is radiated externally with high efficiency. However, the refractive index of the light-emitting layer is so high that the critical angle is very small. As a result, only a part of the light is radiated externally while the rest light is absorbed in the crystal layer which is high in absorptance. Thus, most of the light is converted into heat.